A thermostable antigen (TA) associated with ovarian carcinoma has been identified and partially characterized. The distribution of TA in normal tissues, body fluids, secretions and neoplasms will be further evaluated by a complement fixation assay utilizing purified antibodies from highly absorbed sera. Purification and characterization of TA will facilitate developing a radioimmunoassay capable of detecting TA blood levels in ovarian cancer patients and normal controls. Affinity chromatography on antibody-agarose or Con-A agarose columns as well as conventional gel filtration and ion-exchange techniques will be employed. Purified TA will be characterized by gel electrophoresis, isoelectrofocusing, equilibrium ultracentrifugation, colorimetric carbohydrate analysis and amino acid analysis. High titre specific antisera against purified TA and I235-labeled TA will be utilized in a double antibody radioimmunoassay. Testing of the assay will be carried out on preoperative and postoperative patient sera. Assessment of circulating levels of other ovarian carcinoma-associated antigen A1, A2, A3, A4 will be similarly pursued.